Promotion of breastfeeding is an important child-survival intervention, yet little is known about which promotional strategies are the most effective. We aimed to compare the effects on rates of breastfeeding of two systems for promotion of breastfeeding in Brazil--a hospital-based system and the same system combined with a programme of home visits. In February, 2001, maternity staff from two hospitals in Pernambuco, Brazil, were trained according to the Baby-Friendly Hospital Initiative (BFHI). In a randomised trial between March and August, 2001, 350 mothers giving birth at these hospitals were assigned ten postnatal home visits to promote and support breastfeeding (n=175) or no home visits (n=175). Breastfeeding practices were studied on days 1, 10, 30, 60, 90, 120, 150, and 180 by researchers unaware of group allocation. The primary outcome measure was the rate of exclusive breastfeeding from birth to 6 months. Analyses were by intention to treat. The hospital-training intervention achieved a high rate (70%) of exclusive breastfeeding in the hospitals, but this rate was not sustained at home and at 10 days of age only 30% of infants were exclusively breastfed The patterns of exclusive breastfeeding in the two trial groups for days 10-180 differed significantly (p<0.0001), with a mean aggregated prevalence of 45% among the group assigned home visits compared with 13% for the group assigned none. The BFHI achieves high rates of exclusive breastfeeding in hospital; however, in Brazil at least, the rates fall rapidly thereafter. Reliance on the BFHI as a strategy for breastfeeding promotion should be reassessed. A combination of promotional systems (hospital-based and in the community) is needed.